Project Summary In 1960, 12% of babies worldwide died in their first year of life; this fell to only 3% in 2015. How will infant mortality in the developing world continue to change, as environmental and nutritional factors change? Puzzles remain about today?s heterogeneity in neonatal mortality (NNM), even as changing environmental exposures (such as to heat and humidity) and trends in maternal nutrition portend changes in future global patterns of neonatal death. Policy-making and public health depend on accurate projections of NNM under alternative scenarios. This five-year project will position me to pursue a new research agenda in the population science of NNM in the developing world and to project its future in changing environmental and nutritional contexts. My mentorship will be led by Mentor Joe Potter of the UT PRC (who will teach demographic coursework at UT), with co-Mentor Michel Guillot of the Penn PSC: both are experts on early-life mortality in developing countries. First (Aim 1), during and as a foundational part of training, I will examine demographic literature on neonatal death in developing countries, using new data from surveys and co-Mentor?s related R01 on age of child death. Co-Mentor Michel Guillot?s NICHD-funded project is assembling data on exact age of death. Age at death is informative about the causes of NNM in Aims 2 and 3. Then (Aim 2), I will project consequences of future weather changes for neonatal death, fertility, and population dynamics; to do this, I will first estimate causal effects of changing weather patterns in the developing world on NNM. As part of this Aim and at the heart of this project, I will use demographic methods to project effects of future weather changes. Critically, in the last step of Aim 2, I will use these results (and new training in cohort-level demographic projections from Aim 1) to improve the demographic sub-modules of leading climate-economy models for policy-making; the National Academy of Science recently highlighted such modules as a key research gap in policy-making for environmental public health. Finally (Aim 3), I will project consequences for NNM of changing patterns of maternal nutrition and family size, applying new estimates of the causal effect. Although my training in economics at Princeton University and experience studying child health while living in India are valuable foundations for this research, fulfilling these goals would not be possible without career development in the methods, theories, and insights of demography ? which has not yet been part of my training. These Aims will prepare me to then pursue R01 support as an independent population scientist who will combine economics and demography to inform policy about public health and environmental exposures in the developing world.